Sluth

The sluth are a species of blob creatures of indeterminant taxonomy that live in Tevhetra.
While an individual sluth is immobile and able to do little on its own, sluth are capable are bonding symbiotically with the nervous systems of other complex organisms. The collective entity of a sluth and its host is known as a gumues.

Basic Information

Anatomy

A sluth's body consists of an organic material resembling mud in thickness and texture, bonded together with water and interwoven with nervous cells. If any portion of their body is separated from the rest, the sluth can no longer feel or control that material. If too much of the water in their body freezes or most of the cell bonds in their body are dissolved by excess water, it will kill the sluth.
Sluth naturally process quintessence, which gives them access to an individual pocket dimension. It's also possible that the low level background flow of quintessence may also sustain the sluth as organisms, because honestly their anatomy doesn't make that much sense on its own.
Most sluth are brown, gray, or black, though some have been seen in brownish-green or even grayish purple. If a sluth is in control of their host's body, the host's irises will change color to match the sluth's body, though this can be hard to determine depending on the host's species and appearance.

Genetics and Reproduction

Sluth reproduce asexually and individually by shedding a large portion of their cells into a suitably nutrious patch of soil, ideally with some water and rotting vegetation to feed on. If these cells can absorb enough nutrients within a few nights, they will form into a new sluth. However, if the parent sluth cannot quickly eat enough to restore its own biomass, the loss of so much of its body will likely kill it. Some sluth who are already very weak or unwilling to live anymore may choose to give up all their cells so their death can bring new life. There is also the possibility of a sluth being injured or killed on fertile-enough ground to accidentally produce a new sluth.

Dietary Needs and Habits

On their own, sluth break down and absorb molecules similar to fungi. Along with biomass, they are able to break down some soils.
With a host, a sluth no longer has to feed itself for energy, instead drawing it from their host. As such, hosts must eat much more than they did to sustain just themselves, though the increase of energy spent between the two of them means there usually isn't much of a weight gain. Furthermore, since sluth have no sense of taste in their singular form, many take a huge interest in food and eating. It is custom for a sluth, upon taking a bondmate, to ask their host to share a meal of the host's favorite food with them.

Additional Information

Geographic Origin and Distribution

Pre-Nightfall, the sluth were more widely distributed, though they preferred tropical and subtropical climates that would be warm and wet enough to sustain them. However, the Nightfall and the sudden temperature drop wiped out almost all sluth who were not bonded and thus protected in their pocket dimensions. About a hundred years after the Nightfall, the sluth established the Underbog as their home territory and breeding grounds, and the majority of unbonded sluth live there, though a few have managed to survive in Crystalglade.

Average Intelligence

Sluth seem to be as intelligent as most other sapient species.

Perception and Sensory Capabilities

In their individual form, sluth have extremely limited senses. They can detect changes in temperature and when something is touching their body, but are otherwise unable to perceive anything. They are able to communicate with the nervous system of anything that touches them, including other sluth.

Symbiotic and Parasitic organisms

The sluth can form a symbiotic relation with any organism with a complex nervous system by fully submerging the other being in their body. In this relationship, the sluth and their host share a pocket dimension in which they may switch out parts of their body. Usually, the sluth will remain in the pocket dimension while the host remains in the physical realm, with the sluth able to experience all the host's senses and the two sharing thoughts. However, the host may allow the sluth to take command of their mind and control their body while it is still physically their own. Furthermore, the host may swap out part of their body for the sluth's, such as switching out a limb for a much more flexible blob appendage. The vast majority of sluth prefer to bond with other sapient species, and using a non-sapient body is seen as an emergency resort. 
Pre-Nightfall, there are records of sluth acting as parasites, posing as a mud puddle and waiting for a creature to fall in so they can hijack their body. However, modern sluth place great emphasis on getting an organism's consent before bonding with them and having an equal relationship, and any sluth acting as a parasite is committing a great crime.

Civilization and Culture

Naming Traditions

Sluth give themselves their own names once they're old enough to want one, compounded out of words usually given verbally in Torugk. They may start out with two to four words, usually based off their own physical attributes. Some concepts about themselves, like color, they will only be able to add upon taking a host and sensing them. Sluth will add on words to their name for major life events, such as taking a host. 
The gumues entity will use a shortened handful of syllables from the sluth's full name, usually the first syllable from each word. 
Hosts are not required to change their name while hosting a sluth, other than using the gumues name for the entity as a whole. However, many use a shortened form of their usual name, sometimes even just going by one letter (depending on their native language), to indicate they are not their usual singular self.

Gender Ideals

Sluth have no biological sex and traditionally lack the concept of gender in their culture. A gumues will take on the gender of the host, along with any pronouns, presentation, etc.; individual sluth are usually referred to in neuter language. However, a few sluth have adopted a gender of their own, sometimes even a different one than their host's. This is seen as strange by other sluth but not taboo.

Major Language Groups and Dialects

Among themselves, most hugumues speak Torugk, particularly the Sugung dialect. The sluth also has access to all languages their host speaks.